Magnetic recording media such as magnetic tapes and magnetic disks are now widely used as audio tapes, video tapes, computer tapes, floppy disks and the like, and intensive studies have been conducted to increase the density of the media. In the magnetic recording system, recording and reproducing are carried out by means of a magnetic head. In order to increase the density of the magnetic recording medium, therefore, there are required not only means for improving magnetic characteristics and homogenizing the distribution of a ferromagnetic powder in a magnetic layer, but also means for minimizing the spacing loss produced between the magnetic recording medium and the magnetic head.
For this reason, efforts have been made to make the surface of the magnetic layer as smooth as possible to minimize the spacing loss between the magnetic tape and the magnetic head.
However, as the magnetic surface is finished to a mirror surface and the magnetic tape comes into close contact with the magnetic head, the problem of the strength of the magnetic layer is encountered, namely the exfoliation of the magnetic layer caused by the contact with the magnetic head, the adhesion of the exfoliated magnetic layer to a surface of the magnetic head and the clogging of the magnetic head. On this account, previously abrasive agents about 1 .mu.m in average particle size have been added to the magnetic layer in small amounts to reinforce the magnetic layer.
The particles used as the abrasive agents include Al.sub.2 O.sub.3, Cr.sub.2 O.sub.3, SiC and .alpha.-Fe.sub.2 O.sub.3, and have been added to the surface of the magnetic layer distributed as sparsely as possible, in order to prevent reduced electromagnetic property and to reduce the abrasion of the magnetic head. However, when the increase in density of the magnetic recording medium is further pursued by finely dividing the ferromagnetic powder, increasing coercive force, smoothing the surface of the magnetic layer, and so on, it has become clear that the above-described method is insufficient with respect to the strength of the magnetic tape and the maintenance of the magnetic head under optimum conditions. Then, JP-A-61-57036 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") proposes the distribution of abrasive agents exposed on the surface of the magnetic layer, namely the average number of the abrasive agents per unit area of the magnetic layer, to 0.25 particles/.mu.m.sup.2 or more, in high density recording using a recording wavelength of about 1 .mu.m or less, whereby the abrasive characteristics of the magnetic recording medium are improved and the problems of seizing, discoloration and clogging on the surface of the magnetic head formed of a metal such as Sendust are solved by cleaning due to this improvement. It is possible to improve such properties by this method, but the improvement in reduced audio output due to the damage of the magnetic tape edges caused by the repetition of running is still insufficient.